Coupling systems for connecting trailers or sleds to motor vehicles encounter significant shock and vibrational forces under normal towing conditions. These coupling systems, commonly known as hitches, typically include a rigid body attached to the vehicle linked to another rigid body that is attached to the trailer. As the trailer and vehicle move with respect to one another, the rigid bodies are subject to forces in a number of directions.
A first conventional type of hitch, referred to as a ball hitch, employs a semi-spherical or ball-shaped extension that is supported by a vertically oriented pin. The pin is typically connected either to a rigid tow plate or draw-bar that is in turn, attached to the vehicle. The ball is engineered to engage an opposite coupling, usually mounted on an extension referred to as a tongue, that fits over the top of the ball-shaped extension or otherwise engages the ball. In most conventional circumstances, the ball hitch is attached to the vehicle and the coupler is located on the trailer. This arrangement creates a fairly rigid towing system but allows the trailer to pivot in a horizontal plane with respect to the vehicle and allows limited pivoting movement in a vertical direction. This type of system, like most other hitch engagements, transmits considerable shock and vibration between the trailer and the towing vehicle. As referred to above, the ball hitch may be attached to vehicles using a draw bar tube which allow for easy removal of the ball hitch. A draw bar tube is an elongate member that is received within an opposite draw bar receiving tube. The draw bar receiving tube is typically affixed to the vehicle in a permanent manner or semi-permanent manner using fasteners or by welding.
Another commonly used linking arrangement involves a vertically oriented pin that is provided on the trailer which is received in a collar located on the vehicle. This engagement, commonly referred to as a king-pin engagement, is typically used for towing heavy loads and requires the towing vehicle to bear a significant portion of the trailer weight. In a king-pin arrangement, the pin can pivot within the collar and has some freedom to move within the collar in a vertical direction.
As discussed above, conventional ball hitches are frequently attached to vehicles using a draw bar arrangement. In this type of arrangement, a first hollow receiver tube is mounted to the underside or bumper of the towing vehicle that receives a second draw bar tube. A pair of opposite corresponding holes may be formed on opposite sides of both the receiver tube and draw bar. A connector pin is inserted through the holes to connect the receiver tube and draw bar and thereby prevent rectilinear movement. In some arrangements a trailer hitch assembly or L-shaped tow plate having a conventional form of hitch ball is secured to the draw bar. The connecting pin assembly of the draw bar arrangement allows for a releasable interconnection between the receiver tube of the towing vehicle and the draw bar of the towed trailer.
In each of the examples, constant shock and vibrational forces in various directions will be transmitted from the trailer to the hitch and consequently to the towing vehicle causing wear to the vehicle and hitch, and an uncomfortable ride. The shock and vibrational forces acting on the hitch have numerous sources. For example, upon acceleration or deceleration of the towing vehicle, momentum and inertial forces due to the loads contained on the trailer are longitudinally transmitted from the trailer to the towing vehicle. Uneven and rough surfaces upon which the vehicles are traveling are also a source of both longitudinal and vertical forces acting on the hitch and trailer. It is well known that undue wear and damage to the towing vehicle, the hitch, and the trailer result from the continuous shock and vibration commonly associated with towing a trailer. Vibration and wear are cumulative problems in regard to loosening fasteners and abrasively eroding joints parts and in general on both the vehicle and trailer. In addition to the respective wear on the vehicles, the existence of significant forces being transferred to the vehicle from the trailer makes driving the towing vehicle unpleasant because it adversely effects the ride of the vehicle.
To overcome the problems associated with shock and vibration, trailer hitches with many different dampening mechanisms have been developed and proposed within the related art. Most of the previously proposed hitches with dampening mechanisms have addressed vibration and shock adsorption in either the vertical or longitudinal directions. For example, one such system that address longitudinal shock and vibration is disclosed in U.S. Pat. No. 4,817,978 to James (the '978 patent). The system disclosed in the '978 patent employs a resilient rubber or plastic block assembly within the draw bar tube to dampen fore and aft longitudinal shock and vibration. The '978 patent dampens vibrations at the connector pin connecting the draw bar and receiving tube. U.S. Pat. No. 3,961,813 to Thomas also addresses longitudinal shock but proposes to dampen shock through an assembly at the coupling member itself. The patent to Lovell, U.S. Pat. No. 4,351,542 addresses vertical shock and vibration by the use of coiled springs located in the coupling between the hitch frame and the coupler. Another system disclosed in U.S. Pat. No. 4,773,668 by Muonro, provides for dampening on a vertical axis by means of a resilient bushing inserted into the draw bar of a trailer hitch. A system that has addressed vibration and shock in both the vertical and horizontal directions is disclosed in the Van Vleet Patent, U.S. Pat. No. 5,823,560. The system disclosed by Van Vleet proposes an arrangement of bullet shaped cushions within the draw bar to dampen shock.
Despite the numerous approaches in the related art, there nevertheless remains a need for improved and alternative manners to connect vehicles to trailers that reduce noise and wear of the connecting members.